A hotel invoice is useful for more than just expense reimbursement. My travel is probably 98% leisure, so expense report claims are not a factor in whether I want a paper or electronic invoice. And while it may be old fashioned, I like to review my invoice charges, using the paper copy that is slipped under my door the night before checking out. If I'm travelling without a laptop (and since I'm not on business, I don't need to have it with me), paper is all I use, and I'm not about to try ticking off the charges while reading a invoice that's probably several pages long, on the screen of my phone. As a finance and IT executive, I love technology, but for some things in life, I still like my paper. The higher standard of service would be to offer both options to the traveller.